The curves of circular windows conjure voluptuous softness, a quality that is missing from a lot of rectilinear architecture.

In some cases, such as at 141 Fifth Ave., the oculi, as these windows are known, reinforce curves elsewhere on the building. Originally built for Merchants Bank of New York, the property includes a dome dotted with numerous oculi designed by Robert Maynicke in 1897. A residential conversion is being carried out by Cetra/Ruddy. Manhattan has many oculi, some simple and some multi-paned. While most of these windows are circular, some are elliptical, and they have been used in a wide variety of architectural styles.

The mid-block apartment building known as Eagle Court at 215 W. 84th St. has oculi for all its top-floor windows, as well as two windows on the second floor. The Eagle Court oculi are single-pane, while those found at the corners of the top floor at 1040 Park Ave. are multi-pane. That 1923 building was designed by Delano & Aldrich, and was famous for its penthouse, which was initially occupied by the publisher Cond? Nast. While some oculi top off buildings just beneath the cornices, others are used to "break up" a building's mass. On the six-story apartment building at 1324 Lexington Ave. on the northwest corner of 88th Street, for example, there are pairs of oculi on the second through the sixth floors in the center of the building, just above the entrance.

Many oculi are used to highlight entrances.

The townhouse building at 55 E. 77th St. has an elliptical, multi-paned oculus just to the east of its stoop. Charles Brendon designed the building in the Beaux-Arts style in 1902. It is famous as the house where the CIA colleagues of actor Robert Redford's character were murdered in "Three Days of the Condor." Architect Peter Pennoyer recently oversaw the building's renovation.

The less ornate adjacent building at 57 E. 77th St. was also renovated a few years ago, and it now has a prominent oculus just above its entrance. Andrew Caracciolo was the renovation architect.

Circular openings are more expensive to install than rectilinear ones, but that has not deterred architects in the postwar period.

The attractive, mid-block apartment building at 60 E. 88th St. has a very large oculus on the second floor above its entrance. The 15-story building was designed in 1986 by Beyer Blinder Belle.

Another postwar development that used oculi was the Bromley at 225 W. 83rd St. Designed in 1986 by Costas Kondylis, who then was with Philip Birnbaum & Associates, this red-brick, 308-unit, 23-story building abounds in oculi. Its five top floors have terraces with numerous oculi, and its second floor has even larger oculi on 83rd Street, as well as on the southern section of its frontage on Broadway, where the building extends to 84th Street.

The most prominent oculus in Midtown is just above the entrance to the former AT&T Building, which is now the Sony Building, at 550 Madison Ave. between 55th and 56th streets. Designed by Philip Johnson/John Burgee in 1984, its grand entrance was intended to highlight the great "Spirit of Communications" sculpture that had long stood atop the company's former headquarters building at 195 Broadway.

When AT&T sold the building to Sony, it took the statue to its major corporate campus in New Jersey. In 2000, however, AT&T offered to return the statue to the city. The city could not come up with a plan, and three months later the company decided to keep its marvelous statue.

Oculi can also be found in many religious buildings, such as St. Patrick's Roman Catholic Cathedral, where the large oculi are often known as rose windows due to their stained-glass tracery.

Portholes, the ocean-liner version of oculi, have also been an architectural inspiration. Architect Albert Ledner designed three buildings with such nautical motifs for the National Maritime Union.

One, on the northwest corner of Seventh Avenue and 12th Street, was taken over by St. Vincent's Hospital, which now wants to demolish the structure and replace it with a new hospital building. A second building, facing Ninth Avenue, was converted several years ago into the popular Maritime Hotel.

The third building, situated behind the Maritime Hotel at 346 W. 17th St., is being converted to a hotel and residences by Hampshire House Hotels. It has a slanted facade on 17th Street with more than 100 portholes. It eventually was taken over by Covenant House, and last year Hampshire House Hotels commissioned Handel Architects to create 270 transient hotel rooms and 74 apartment hotels on the property.

Frank Fusaro of Handel Architects told the land use committee of Community Board 4 last year that more portholes would be added to create a "quirky syncopation" for the facade. The project received a partial permit from the Department of Buildings this month.

This article was previously published by the New York Sun.

www.nysun.com/real-estate/why-be-square/70129/